Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FUNCTIONAL FLLfID ADDITIVES FOR ACID COPPER ELECI'ItOPLATING BATHS
Technical held
The present application relates to high acid/low metal copper electroplating
baths. More
particularly, the present invention relates to functional fluid additives for
such solutions.
Background of the Invention
In recent years, many advances in the area of electroplating of copper
deposits have
produced increasingly superior properties in ductility, leveling and other
properties of copper
deposits. produced from high metal low acid electroplating baths. Primarily,
these advances have
been in the use of various additions to such copper electroplating baths. Most
notably, the
additions of divalent sulfur compounds and alkylation derivativcx of
polyethylene imines have
resulted in improved leveling in decorative copper plating. F~amples of these
types of additions
are shown in U.S. Patent No. 4,336,114 to Mayer et al.; U.S. Patent No.
3,267,010 to Creutz et
al.; U.S. Patent No. 3,:328,273 to Creutz; U.S. Patent No. 3,770,598 to Creutz
et al.; and U.S.
Patent No. 4,109,176 to Creutz et al. 'While these additions have found
commercial acceptance
in plating of high metal low acid copper baths, they have not solved problems
inherent in
electroplating of parts from high acid/low metal, copper baths. U.S. Patent
No. 4,374,709 to
Combs is a process for ;plating of copper on substantially non-conductive
substrates utilizing high
acid/low metal copper baths. While this process has been a great advance in
the art of plating
of non-conductive substrates, there remains a need for improved and simplified
plating of metallic
and non-conductive substrates and also in troublesome plating functions such
as: plating of
intricate parts with low current density areas; circuit board plating and
other plating of substrates
with surface imperfections; and in barrel plating applications:
For instance, barrel plating has been fraught with problems with regard to
copper plating
of parts. Typically, barrel plating operations have suffered from lack of
proper adhesion between
the built up layers of copper plate on the parts. Thus, barrel plating of
parts has not been
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suitahle from a production or sales standpoint. Copper plating applied on
intricately shaped parts
has been fraught with adhesion problems during thermal expansion cycles;
thickness deficiencies
in low current density areas; and suffer because of the low ductility of the
deposit produced.
Additionally, with respect to nonconductive plating of perforated circuit
board material, or other
substrates with substantial surface imperfections, the leveling properties of
past plating methods
have not been sufficient to overcome such surface imperfections in these
substrates.
Thus, it has been a goal in the art to produce an electroplating bath and
process which
provides improved ductility copper deposits; has superior leveling and
adhesion characteristics; and
which has improved throwing power, beneficial in areas of low current density.
SummarK of the Invention
In accordance W th the above goals and objectives, in the present invention
there is
provided an improved bdgh acid/low copper bath and process for plating of
copper. The process
comprises the use of effective amounts of a functional fluid having triple
ether functionality, in
the electroplating bath, for improved copper deposits.
Compositions in accordance with the present invention provide improved copper
plating
in low current density areas and have superior gap and surface imperfection
filling capabilities,
for plating across gaps ~or other imperfections in substrates, while providing
good adhesion and
ductility properties. Additionally, utilizing the compositions of the present
invention there is
provided an improved acid copper bath whereby barrel plating of parts can be
accomplished with
acid copper baths.
Description of the Preferred Embodiments
In accordance W th the composition and method aspects of the present
invention, the
invention is operable in aqueous acidic copper plating baths wherein high
concentrations of acid
are used with low copper ion concentrations for electroplating.
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Aqueous acidic copper plating baths of the
present invention are typically of the acidic copper
sulfate type or acidic copper fluoroborate type. In
accordance with conventional practice, aqueous acidic
copper sulfate bathe typically contain from about 13 to
about 45 g/1 o:E copper ions with preferred concentrations
of from about 25 to about 35 g/1. Acid concentrations in
these baths t:ypica:Lly range from about 45 to about
252 g/1 of acid and preferably amounts of from about 150
to about 220 g,/1 acid. Fluoborate solutions would use the
same ratio of acid to metal in the bath. The additives of
the present invention are particularly advantageous in
such low coppe:r ion/high acid solutions.
In accordance with the method aspects of the
present invention, l:he acid copper plating baths of the
present invention are typically operated at current
densities ranging from about 5 to about 60 amperes per
square foot (ASF) although current densities as low as
about 0.5 ASF to as high as about 100 ASF can be employed
under appropriate conditions. Preferably, r_urrent
densities of from about 5 to about 50 ASF are employed.
In plating conditions in which high agitation is present,
higher current densities ranging up to about 100 ASF can
be employed as necessary and for this purpose a
combination o:E air agitation, cathode movement and/or
solution pumping may be employed. The operating
temperature of the plating baths may range from about
15°C to as high as about 50°C with temperatures of about
21°C to about 36°C f>eing typical.
The aqueous acidic sulfate bath also desirably
contains chloride ions which are typically present in
amounts of less than about 0.1 g/1. The method and
compositions of the present invention are compatible with
commonly utilized brightening agents such as polyethylene
imine derivative quaternary such as disclosed in U.S.
Patent No. 4,,110,776 and disulfide additives such as
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those disclosed in U.S. Patent No. 3,267,010.
Additionally, the alkylation derivatives of polyethylene
imines such as that disclosed in U.S. Patent
No. 3,770,598 may also be utilized as set forth in that
patent. Other additions may include propyl disulfide
phosphonates and R-mercapto alkyl sulfonate type
derivatives with S-2 functionality. In addition, when the
present invention is utilized in a composition for
plating of electronic circuit boards or the like the
additives set forth in U.S. Patent No. 4,336,114 may be
utilized as set forth therein and known in the art. High
acid/low metal plating baths and suitable additives are
set forth in U.S. Patent No. 4,374,409.
In accordance with the composition and process
of the present :invention effective amounts of a
functional fluid having triple ether functionality are
utilized for providing superior ductility, leveling over
substrates and including gap filling properties
heretofore unrealized in such plating solutions.
Functional fluids useful in the present invention include
a polymer having an alkyl ether end group with propoxy
and ethoxy functionality in the main chain. The
functional fluids suitable for use in the present
invention are bath soluble. Typically, functional fluids
useful in the present invention are characterized by the
following formula:
(R1~~R2 3~R3~R4
wherein:
R2 <~nd R;; are interchangeable in their order
within the above formula and preferably are blocks of
either R2 or R3, however, random mixtures of R2 or R3 is
also possible;
R1 i_s selected from the group consisting of an
ether group derived from an alcohol moiety having from
about 4 to about 10 carbon atoms; an ether group derived
from a bisphenol A moiety; an epoxy derived ether moiety
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with 4-6 carbon atoms or mixtures thereof, and m is
selected to bE: from. about 1 to about 10 but preferably
from 1 to 3.
R2 is selected from the group consisting of:
~ H3 ~H3 ~H3
CH2-CH2-O-; CH2-CH2-O-; CH2-CH2-CH2-0-; ~H2-O-
H3
and mixtures thereof; and
R3 is selected from the group consisting of
CH3
~:H2-O-: CH2-CH2-O-;
and mixtures thereof; and
R4 is selE~cted from the group consisting of H,
CH3, an alky=~ group having 1 to 12 carbon atoms, a
hydroxyalkyl group having 1 to 12 carbon atoms, an ether
group having 1 to 3 carbon atoms, a polar alkyl group
having 1 to 12 carbon atoms, an ionic constituent or an
alkyl group having 1 to 12 carbon atoms and an ionic
constituent such as carboxylic acid, sulfate, a
sulfonate, a phosphonate or alkali metal ion and mixtures
thereof wherein n a:nd o are selected such that the ratio
of n to o is from about 1/2:1 to about 1:30. Preferably,
the ratio of n to o is from about 1:1 to 1:20. The R4
moiety may include a sodium or other alkali ion for
forming a salt. as well as ammonium ions.
The functional fluid of the present invention
generally has a molecular weight of from about 500 to
10,000. Preferred molecular weights of the functional
fluids are from about 1,000 to about 2,500 in the
embodiments set forth below.
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The ;preferred R1 moiety is a butyl ether group
derived from butyl alcohol. However, longer chain alkyl
ether groups may be used as set forth above. Use of
functional fluids wherein R1 is derived from some of the
longer chain alcohols, for instance having 9 or 10 carbon
atoms, may result in foaming conditions in the bath.
However, if this occurs, the quantity of the fluid may be
reduced to alleviate foaming conditions.
As Examples, typical functional fluids useful
in the present. invention are commercially available from
Union Carbide' as UCON~HB and H series fluids.
Particularly, preferred functional fluids include 50 HB
and 75 H series fluids such as 50 HB 660; 50 HB 5100;
50 HB 260; 75 H 450; 75 H 1400; and 75 H 90,000.
The methods and compositions of the present
invention find advantageous use in four related but
distinct areas of copper plating. These four areas
include acid copper' strikes; acid copper circuit board
plating; barrel plating; and high throw decorative
plating applications.
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When used in a bright copper strike bath, generally, from about 1 mg/1 to
about 1000 mgh
of the functional fluid is utilized in baths for bright copper strikes.
Typically, such baths require
use of fiom about 1 m~g/1 to about 700 mg/1 with preferred ranges being from
about 3 mg/1 to
about 120 mg/1 of the functional fluid. Such a process when used in bright
copper strikes allows
increased leveling and ;adhesion in low current density areas such that
intricate shaped parts may
be more advantageously plated utilizing the process and methods of the present
invention in high
acid/low copper solutions. Typically, when utilized as a bright copper strike
method greater
amounts of disulfide preferably in the range of from about 1 to about 30 mg/1
of a disulfide with
preferred ranges being from about 5 to 15 mg/1. Brighteners such as the
quaternary polyethylene
imines are useful in quantities of from about 1 to about 5 mg/I and preferably
1 to 2 mg/1 in such
solutions.
With respect to electronicx grade plating operations such as plating of
perforated circuit
board and the like, the; present process produces fme grain to satin grain
type plates and is an
improvement in leveling out over surface imperfections and produces uniform
copper coatings in
the holes with excellent deposit physical properties.
Thus, for electronics plating applications such as functional fluids are
utilized in quantities
generally from about 20 to about 2000 mg/1. Typically 40 to about 1500 mg/1
would be utilized.
In a preferred embodiment of the present invention 120 to about 1000 mg/1
functional fluid is
utilized. Although not necessary, in a preferred embodiment from about 0.2 to
about .20 mg/1 of
sulfide compounds are useful in baths of such electronic plating processes.
Also, small amounts
of brighteners such as quaternary polyethylene imines can be utilized in
quantities of fiom about
1 to about 5 mg/t in the process of the present invention.
With respect to barrel plating applications of the present invention, in the
past it has been
commercially impractical to utilize barrel plating for copper strikes and the
like in high acid/low
copper solutions. Hov~rever, in the advantageous use of the present invention
it is now possible
to utilize barrel plating for cropper plating of smaller intricate parts and
the like. In barrel plating
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systems the copper strike typically is preferred to be brighter and ductility
is not as important as
in some of the other applications. However, layered adhesion in barrel plating
is critical. Prior
to the present invention layer adhesion has been a serious problem which made
such plating
operations impractical. In the present invention this is corrected by
utilizing the functional fluid
as set forth above in quantitiex of from about 10 to about 1200 mg/1.
Typically from about 40 to
700 mg/1 and preferably 60 to 600 mg/1 are utilized in barrel plating of parts
in the present
invention. When utilizing functional fluids in any of the baths set forth
above, it is a general rule
that greater quantities of lower molecular weight polymers are needed for
proper performance,
whereas, if higher molecular weight functional fluids are used smaller
quantities may be utilized
for achieving the desired rexults.
The functional fluid additions of the present invention are also advantageous
in that they
work well in decorative baths including common brighteners, dyes and the like
used in such baths.
Thus, the prbsent invention can be used in low metal/high acid production
.systems already in
place for achieving improved results.
Further understanding of the present invention will be had with reference to
the following
examples which are set forth herein for purposes of illustration but not
limitation.
EXAMPLE I
Co-pper Strike
A copper strike; bath utilizing 175 gel of copper sulfate pentahydrate; 195
g/t sulfuric acid;
60 mg/1 chloride-ion; amd 40 mg/l functional fluid ('MW 4000) is provided
Electroless nickel
plated ABS panels are plated with air agitation at 15 ASF with a bath
temperature of about 80°F.
The copper strike deposits on these parts were fine grained and uniform.
'Butyl ether-polypropoxyether-polyet);oxyether with hydroxy end groups.
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EXAMPLE II
Decorative
To a bath as se;t forth above was added 20 mg/1 sodium 3, 3 sulfo propane 1,1
disulfide;
9 mg/1 lanus Green Dye. The parts were plated with air agitation at 30 ASF
with a 92°F bath
temperature. The copper deposit on the parts was uniformly lustrous with all
base metal
imperfections leveled out after 30 minutes of bath operation.
Plating of Circnsit Boards
A plating bath was prepared using 67.5 g/t copper sulfate pentahydrate; 172.5
g/1
concentrated sulfuric acid; 60 mg/1 chloride-ion; and 680 mg/l butoxy
propyloxy ethyloxy polymer
functional fluid (MW 1100). A copper clad laminate circuit board was plated at
24 ASF with air
agitation at 75°F. The; copper deposit was uniform, semi-bright, fine
grained and very ductile.
The deposit passes 10 thermal-shock cycles without separation, showing the
superior physical
properties of the copper deposit.
EXAMPLE IV
Acid Comer Strike
A bath was prepared utilizing 75 g/1 copper sulfate pentahydrate; 187.5 g/I
concentrated
sulfuric acid; 65 mg/1 chloride ian; 80 mg/l butyl-oay-propyloxy-ethyloay
polymer functional fluid
(MW 1100); 1 mg/1 ~3-sulfopropyl]zdisulfide sodium salt; 1.5 mg/1 poly
(alkanol quaternary
ammonium salt as per U.S. Patent No. 4,110,176). Electroless copper plated ABS
panels were
plated utilizing 15 ASF at a temperature of 85°R
The strike produced had good ductility and adhesion qualities even in low
current density
areas and would readily accept subsequent nickel and chromium deposits
readily.
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EXAMPLE V
Barrel Platine l:.xa_ mple
A barrel plating; bath was formulated utilizing 75 g/1 copper sulfate
pentahydrate; 195 g/1
concentrate sulfuric acid; 75 ppm (75 mg/1) chloride-ion; 100 mg/l functional
fluid (MW 1700); 2
mg/13,3 sulfopropyl disulfide; 1 mg/1 polyethylene quaternary. Plating of
small steel parts having
a cyanide free alkaline: copper strike was accomplished at 7-10 ASF average
cathode current
density. The plating on the parts was bright, uniform, with good leveling and
adhesion between
layers. These parts will accept subsequent nickel and chromium deposits
readily. The copper
deposit was very ductile allowing for thick electroforming applications.
EXAMPLE VI
Baths are prepared utilizing as follows: (a) 20 g/1 copper ions; 225 g/1
sulfuric acid; (b) 14
g/1 copper ions 45 g/1 sulfuric acid; (c) 45 g/1 copper; 100 g/l sulfuric
acid; and (d) 15 g/1 copper
ions; 262 g/1 sulfuric acid.
These baths arE; then utilized to form copper plating baths of the present
application by
adding from 1 to 2,000 mg/1 of functional fluids having butoxy, ethoxy and
propoxy functionality
with molecular weight:. from 500 to 10,000. Electroplated parts produced are
found to have
copper plating producing fine grained deposits with good adhesion, ductility
and throwing
properties.
EXAMPLE VII
Printed Circuit Boards
A plating bath was prepared using 69 g/1 copper sulfate pentahydrate; 225 g/1
sulfuric acid,
and 80 mg;/1 chloride. To this bath is added 700 mg/l of 2,2 dimethyl 2,2
diphenol propylene
reacted with 12 moles propylene oxide followed by 20 moles of ethyleneoxide,
sulfated to 30-50%
of the final content of end hydroxy groups, as an ammonium salt. Copper clad
laminate circuit
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boards are processed at 20 ASF for 1 hour, the deposit was fine grained,
ductile, uniform, and
exhibited excellent low current density thickness.
While the abovc; description constitutes the preferred embodiments it is to be
appreciated
that the invention is suscept'ble to modification, variation and change
without departing from the
proper scope and fair rneaning of the accompanying claims.
